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Predicting climate

Just when everyone was getting sick of explaining that climate models are producing projections not predictions per se, it seems that some of them are indeed producing predictions. There’s a paper (pdf) in Science from a team at the Hadley Center that shows how using real initial conditions improves the accuracy of ten year climate forecasts. They do a bit for hindcasting first, looking at historical data and comparing model runs with real initial conditions with run-of-the-mill runs. Then they do some prediction. This prediction is being treated as saying that we’re at the end of a little plateau, and that at the end of this decade things will warm up further, giving a run of years in the early 2010s where the chances for new global records are good. Quirin Schiermeier wrote a story on this for news@nature, reporting that the modelling community seems pretty impressed. Here’s a bunch more coverage (88 pieces at the time of googling), and for those with a subscription to Science here’s the estimable Dick Kerr, who had longer to write the story than the rest of us…

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  1. Report this comment

    JamesG said:

    Difficult to keep up isn’t it? We were told that solar had no effect on climate this century but we are now told yes it had an effect up to 1985. We were told that there was no plateauing of temperature, (in counter to the claims of Lindzen, Ball, Carter etc) but we are now told yes it is plateauing after all. We were told the GISS data was robust and it turns out not to be. We’re told projections are not meant to be predictions. Tell the enviro journalists please because they think it’s the same thing.

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    Chris Exley said:

    Like many, I have little doubt that the world is undergoing a substantial period of climate change at this moment in time. I also have little doubt that the activities of humans contribute to this both directly and indirectly. I remain to be completely convinced that the activities of humans (in addition to breathing) are the primary driving force behind the changes we are observing. However, one thing really puzzles me and I am sure that there is someone out there who can explain this to me. How does a proportionately large but actually very small increase in atmospheric carbon dioxide cause an increase in atmospheric temperature? How does the concentration of carbon dioxide drive temperature change? Or am I missing the point?

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    D Craig said:

    A large proportion of the scientific community also has the same problem with CO2 being a driver of climate. Antarctic ice core data do appear to show that it is in fact the other way round – atmospheric CO2 is forced by rising temperature.

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    RichardB said:

    The good folk at realclimate.org have dealt with these comments before.

    We know that CO2 is a forcing for temperature because of the physical properties of CO2 – it absorbs infrared radiation, as has been known a long time.

    ‘Atmospheric CO2 is forced by rising temperature’ is true, but that is in no way contradictory to ‘Rising temperature is forced by increasing atmospheric CO2’. Both are true.

    What the data show is that we have never been in the situation before of a large rise in CO2 (largely anthropogenic) preceding a temperature rise. Therefore we can expect a temperature rise (although this will be influenced by other processes).

    And who says solar radiation doesn’t affect the climate? Any climate scientist will tell you it’s the biggest influence! But what it doesn’t explain is the rising global average temperature since 1985.

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    Chris Exley said:

    Having returned from a brief holiday I had hoped to find at least one solution to my question as to how small changes in atmospheric carbon dioxide drive increases in global temperature. Surely there are many out there who can elicidate upon this? Afterall, is it not at the centre of the whole discussion of how human activities are responsible for climate change?

    Just point me in the right direction!

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    Chris Exley said:

    Thanks to the posting from RichardB but..where is the science…these are not scientific explanations of how a comparatively (compare to 2000 million years ago, for example!!)very small increase in atmospheric carbon dioxide could result in significant changes in global temperature. Where are the experiments that demonstrate the ‘effects’ suggested by RichardB? We need to deal in peer-reviewed research in dealing with these discussions not opinions on websites. I am purporting nothing. I just do not understand the mechanism!

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    coby said:

    Chris,

    You might find Spencer Weart’s discovery of global warming site useful:

    https://www.aip.org/history/climate/index.html

    One reason it is hard to find citations of the basic science in current discussions is because it is so well and long established that no feels the need to substantiate it. Statements like “CO2 absorbs IR” or “CO2 is an important GHG” are so well established that it is not necessary to provide citations.

    If you wish to convince yourself of these things then you need to get your hands on some basic atmospheric chemistry or climatology texts. Oh, the IPCC reports do cover the basic mechanisms of climate, check the 2001 material it is presented in HTML and easier to navigate.

    https://www.grida.no/climate/ipcc_tar/wg1/index.htm

    HTH!

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    Erl Happ said:

    On the habitability of the planet.

    Temperatures of less than 10°C during the day can harm the photosynthetic apparatus of plants. Plant growth is optimal at about 25°C. Unless night time temperatures remain sufficiently warm plant productivity is compromised because plant metabolism requires warmth on a 24 hour basis. Extension of plant parts is greatest during the night when moisture stress is least. Plants depend upon atmospheric carbon dioxide for the creation of carbohydrate via photosynthesis. The agricultural productivity of the planet directly depends upon temperature and the maintenance of a supply of carbon dioxide. Currently the concentration of carbon dioxide is sub optimal and plants suffer greater water loss than would be the case if its concentration were higher.

    The estimate for the average temperature of the Earth is 15°C. This is cool from the plant growth perspective. Let’s assume however, that this is the most desirable temperature.

    The part of the Earth that currently experiences a heat surplus as measured by that proportion where temperature is greater than 15°C is small. Away from the equator the zone of heat surplus may be confined to the dayside portion and may not even persist during daylight hours …

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